Question

which term of an A.P is 70, if the first term is 120 and the common difference is -5

Answer 1

✨Answer:

11 term is 70.

✨ Step-by-step explanation:

Let 70 be Tn.

Then,

➡️ Tn = a + (n - 1)d

➡️ 70 = 120 + (n - 1) - 5

➡️ 70 = 120 - 5n + 5

➡️ 65 = 120 - 5n

➡️ 5n = 120 - 65

➡️ 5n = 55

➡️ n = 11

70 is the 11 th term of given ap in which first term a is 120 and common difference d is - 5.

Answer 2

let, nth term of AP is 70.

Also, a=120

d=-5

we know thay,

$n \: th \: trem \: of \: ap = a + (n - 1)d \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 70= 120 + (n - 1) - 5 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 70 = 120 - 5n + 5 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 70 = 125 - 5n \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 5n = 125 - 70 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 5n = 55 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: n = \frac{55}{5} \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: n = 11 \\ \\ hence \: 11th \: term \: will \: be \: 70.$

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